1. Technical Field
The present invention relates to an apparatus, which measures a polarization state of transmitted light where linearly polarized light is transmitted through a subject, or the like.
2. Background Technology
It is possible to know the state of a substance without directly touching the substance, by measuring light which is transmitted through the substance. For example, when linearly polarized light passes through an optically active substance such as glucose, a property referred to as optical rotation where the polarization plane thereof is rotated is known. The linearly polarized light is a combination of left and right circularly polarized light. Since the refractive indexes of the left and right circularly polarized light are different, a difference occurs in the speed of the left and right circularly polarized light which travels in the substance. As a result, a phase difference occurs in the left and right circularly polarized light which passes through a subject and the polarization plane is rotated in the light which is composed of the left and right circularly polarized light.
In addition, when linearly polarized light is incident onto a substance (a chiralic substance) where the absorption rates with regard to left and right circularly polarized light are different, the amplitude of the light of the left and right circularly polarized light (the magnitude of the light) changes due to a characteristic referred to as circular dichroism. Due to optical rotation and circular dichroism, the transmitted light which is transmitted through the substance becomes elliptically polarized light where the polarization plane has been rotated from when incident. The techniques for measuring the polarization state which focuses on optical rotation and circular dichroism are disclosed in, for example, patent literature 1 to 3.
International Patent Publication No. 2007/029652 (Patent Document 1), Japanese Laid-open Patent Application No. 2007-93289 (Patent Document 2) and Japanese Laid-open Patent Application No. 2007-340833 (Patent Document 3) are examples of the related art.